Repository of MRI-derived models of the breast with single and multiple benign and malignant tumors for microwave imaging research.

The diagnosis of breast cancer through MicroWave Imaging (MWI) technology has been extensively researched over the past few decades. However, continuous improvements to systems are needed to achieve clinical viability. To this end, the numerical models employed in simulation studies need to be diversified, anatomically accurate, and also representative of the cases in clinical settings. Hence, we have created the first open-access repository of 3D anatomically accurate numerical models of the breast, derived from 3.0T Magnetic Resonance Images (MRI) of benign breast disease and breast cancer patients. The models include normal breast tissues (fat, fibroglandular, skin, and muscle tissues), and benign and cancerous breast tumors. The repository contains easily reconfigurable models which can be tumor-free or contain single or multiple tumors, allowing complex and realistic test scenarios needed for feasibility and performance assessment of MWI devices prior to experimental and clinical testing. It also includes an executable file which enables researchers to generate models incorporating the dielectric properties of breast tissues at a chosen frequency ranging from 3 to 10 GHz, thereby ensuring compatibility with a wide spectrum of research requirements and stages of development for any breast MWI prototype system. Currently, our dataset comprises MRI scans of 55 patients, but new exams will be continuously added.

Inverse Design of Self-Folding 3D Shells.

Self-folding is an emerging paradigm for the inverse design of three-dimensional structures. While most efforts have concentrated on the shape of the net, our approach introduces a new design dimension-bond specificity between the edges. We transform this design process into a Boolean satisfiability problem to derive solutions for various target structures. This method significantly enhances the yield of the folding process. Furthermore, by linearly combining independent solutions, we achieve designs for shape-shifting nets wherein the dominant structure evolves with varying external conditions. This approach is demonstrated through coarse-grained simulations on two examples of triangular and square nets capable of folding into multiple target shapes.

Lattice Boltzmann simulation of deformable fluid-filled bodies: progress and perspectives.

With the rapid development of studies involving droplet microfluidics, drug delivery, cell detection, and microparticle synthesis, among others, many scientists have invested significant efforts to model the flow of these fluid-filled bodies. Motivated by the intricate coupling between hydrodynamics and the interactions of fluid-filled bodies, several methods have been developed. The objective of this review is to present a compact foundation of the methods used in the literature in the context of lattice Boltzmann methods. For hydrodynamics, we focus on the lattice Boltzmann method due to its specific ability to treat time- and spatial-dependent boundary conditions and to incorporate new physical models in a computationally efficient way. We split the existing methods into two groups with regard to the interfacial boundary: fluid-structure and fluid-fluid methods. The fluid-structure methods are characterised by the coupling between fluid dynamics and mechanics of the flowing body, often used in applications involving membranes and similar flexible solid boundaries. We further divide fluid-structure-based methods into two subcategories, those which treat the fluid-structure boundary as a continuum medium and those that treat it as a discrete collection of individual springs and particles. Next, we discuss the fluid-fluid methods, particularly useful for the simulations of fluid-fluid interfaces. We focus on models for immiscible droplets and their interaction in a suspending fluid and describe benchmark tests to validate the models for fluid-filled bodies.

Optimal face-to-face coupling for fast self-folding kirigami.

Kirigami-inspired designs can enable self-folding three-dimensional materials from flat, two-dimensional sheets. Hierarchical designs of connected levels increase the diversity of possible target structures, yet they can lead to longer folding times in the presence of fluctuations. Here, we study the effect of rotational coupling between levels on the self-folding of two-level kirigami designs driven by thermal noise in a fluid. Naturally present due to hydrodynamic resistance, we find that this coupling parameter can significantly impact a structure's self-folding pathway, thus enabling us to assess the quality of a kirigami design and the possibility for its optimization in terms of its folding rate and yield.

Environmental memory boosts group formation of clueless individuals.

The formation of groups of interacting individuals improves performance and fitness in many decentralised systems, from micro-organisms to social insects, from robotic swarms to artificial intelligence algorithms. Often, group formation and high-level coordination in these systems emerge from individuals with limited information-processing capabilities implementing low-level rules of communication to signal to each other. Here, we show that, even in a community of clueless individuals incapable of processing information and communicating, a dynamic environment can coordinate group formation by transiently storing memory of the earlier passage of individuals. Our results identify a new mechanism of indirect coordination via shared memory that is primarily promoted and reinforced by dynamic environmental factors, thus overshadowing the need for any form of explicit signalling between individuals. We expect this pathway to group formation to be relevant for understanding and controlling self-organisation and collective decision making in both living and artificial active matter in real-life environments.

Effect of droplet deformability on shear thinning in a cylindrical channel.

Droplets suspended in fluids flowing through microchannels are often encountered in different contexts and scales, from oil extraction down to microfluidics. They are usually flexible and deform as a product of the interplay between flexibility, hydrodynamics, and interaction with confining walls. Deformability adds distinct characteristics to the nature of the flow of these droplets. We simulate deformable droplets suspended in a fluid at a high volume fraction flowing through a cylindrical wetting channel. We find a discontinuous shear thinning transition, which depends on the droplet deformability. The capillary number is the main dimensionless parameter that controls the transition. Previous results have focused on two-dimensional configurations. Here we show that, in three dimensions, even the velocity profile is different. To perform this study, we improve and extend to three dimensions a multicomponent lattice Boltzmann method which prevents the coalescence between the droplets.

Steering self-organisation through confinement.

Self-organisation is the spontaneous emergence of spatio-temporal structures and patterns from the interaction of smaller individual units. Examples are found across many scales in very different systems and scientific disciplines, from physics, materials science and robotics to biology, geophysics and astronomy. Recent research has highlighted how self-organisation can be both mediated and controlled by confinement. Confinement is an action over a system that limits its units' translational and rotational degrees of freedom, thus also influencing the system's phase space probability density; it can function as either a catalyst or inhibitor of self-organisation. Confinement can then become a means to actively steer the emergence or suppression of collective phenomena in space and time. Here, to provide a common framework and perspective for future research, we examine the role of confinement in the self-organisation of soft-matter systems and identify overarching scientific challenges that need to be addressed to harness its full scientific and technological potential in soft matter and related fields. By drawing analogies with other disciplines, this framework will accelerate a common deeper understanding of self-organisation and trigger the development of innovative strategies to steer it using confinement, with impact on, e.g., the design of smarter materials, tissue engineering for biomedicine and in guiding active matter.

Dispersion of activity at an active-passive nematic interface.

Efficient nutrient mixing is crucial for the survival of bacterial colonies and other living systems known as active nematics. However, the dynamics of this mixing is non-trivial as there is a coupling between nutrients concentration and velocity field. To address this question, we solve the hydrodynamic equation for active nematics to model the bacterial swarms coupled to an advection-diffusion equation for the activity field, which is proportional to the concentration of nutrients. At the interface between active and passive nematics the activity field is transported by the interfacial flows and in turn it modifies them through the generation of active stresses. We find that the dispersion of this conserved activity field is subdiffusive due to the emergence of a barrier of negative defects at the active-passive interface, which hinders the propagation of the motile positive defects.

The role of disorder in the motion of chiral active particles in the presence of obstacles.

The presence of obstacles is intuitively expected to hinder the diffusive transport of active particles. However, for chiral active particles, a low density of obstacles near a surface can enhance their diffusive behavior. Here, we study numerically the role that disorder plays in determining the transport dynamics of chiral active particles on surfaces with obstacles. We consider different densities of regularly spaced obstacles and distinct types of disorder: noise in the dynamics of the particle, quenched noise in the positions of the obstacles as well as obstacle size polydispersity. We show that, depending on the type and strength of the disorder, the presence of obstacles can either enhance or hinder transport, and discuss implications for the control of active transport in disordered media.

Cell Response in Free-Packed Granular Systems.

The study of the interactions of living adherent cells with mechanically stable (visco)elastic materials enables understanding and exploitation of physiological phenomena mediated by cell-extracellular communication. Insights into the interaction of cells and surrounding objects with different stability patterns upon cell contact might unveil biological responses to engineer innovative applications. Here, we hypothesize that the efficiency of cell attachment, spreading, and movement across a free-packed granular bed of microparticles depends on the microparticle diameter, raising the possibility of a necessary minimum traction force for the reinforcement of cell-particle bonds and long-term cell adhesion. The results suggest that microparticles with diameters of 14-20 µm are prone to cell-mediated mobility, holding the potential of inducing early cell detachment, while objects with diameters from 38 to 85 µm enable long-lasting cell adhesion and proliferation. An in silico hybrid particle-based model that addresses the time-dependent biological mechanisms of cell adhesion is proposed, providing inspiration for engineering platforms to address healthcare-related challenges.

Model for active particles confined in a two-state micropattern.

We propose a model, based on active Brownian particles, for the dynamics of cells confined in a two-state micropattern, composed of two rectangular boxes connected by a bridge, and investigate the transition statistics. A transition between boxes occurs when the active particle crosses the center of the bridge, and the time between subsequent transitions is the dwell time. By assuming that the rotational diffusion time τ is a function of the position, some experimental observations are qualitatively recovered as, for example, the shape of the survival function. τ controls the transition from a ballistic regime at short time scales to a diffusive regime at long time scales, with an effective diffusion coefficient proportional to τ. For small values of τ, the dwell time is determined by the characteristic diffusion timescale which is constant for very low values of τ, when the rotational diffusion is much faster than the translational one and decays with τ for intermediate values of τ. For large values of τ, the interaction with the walls dominates and the particle stays mostly at the corners of the boxes increasing the dwell time. We find that there is an optimal τ for which the dwell time is minimal and its value can be tuned by changing the geometry of the pattern.

Development of 3D MRI-Based Anatomically Realistic Models of Breast Tissues and Tumours for Microwave Imaging Diagnosis.

Breast cancer diagnosis using radar-based medical MicroWave Imaging (MWI) has been studied in recent years. Realistic numerical and physical models of the breast are needed for simulation and experimental testing of MWI prototypes. We aim to provide the scientific community with an online repository of multiple accurate realistic breast tissue models derived from Magnetic Resonance Imaging (MRI), including benign and malignant tumours. Such models are suitable for 3D printing, leveraging experimental MWI testing. We propose a pre-processing pipeline, which includes image registration, bias field correction, data normalisation, background subtraction, and median filtering. We segmented the fat tissue with the region growing algorithm in fat-weighted Dixon images. Skin, fibroglandular tissue, and the chest wall boundary were segmented from water-weighted Dixon images. Then, we applied a 3D region growing and Hoshen-Kopelman algorithms for tumour segmentation. The developed semi-automatic segmentation procedure is suitable to segment tissues with a varying level of heterogeneity regarding voxel intensity. Two accurate breast models with benign and malignant tumours, with dielectric properties at 3, 6, and 9 GHz frequencies have been made available to the research community. These are suitable for microwave diagnosis, i.e., imaging and classification, and can be easily adapted to other imaging modalities.

Combining experiments and in silico modeling to infer the role of adhesion and proliferation on the collective dynamics of cells.

The collective dynamics of cells on surfaces and interfaces poses technological and theoretical challenges in the study of morphogenesis, tissue engineering, and cancer. Different mechanisms are at play, including, cell-cell adhesion, cell motility, and proliferation. However, the relative importance of each one is elusive. Here, experiments with a culture of glioblastoma multiforme cells on a substrate are combined with in silico modeling to infer the rate of each mechanism. By parametrizing these rates, the time-dependence of the spatial correlation observed experimentally is reproduced. The obtained results suggest a reduction in cell-cell adhesion with the density of cells. The reason for such reduction and possible implications for the collective dynamics of cancer cells are discussed.

Inheritances, social classes, and wealth distribution.

We consider a simple theoretical model to investigate the impact of inheritances on the wealth distribution. Wealth is described as a finite resource, which remains constant over different generations and is divided equally among offspring. All other sources of wealth are neglected. We consider different societies characterized by a different offspring probability distribution. We find that, if the population remains constant, the society reaches a stationary wealth distribution. We show that inequality emerges every time the number of children per family is not always the same. For realistic offspring distributions from developed countries, the model predicts a Gini coefficient of G ≈ 0.3. If we divide the society into wealth classes and set the probability of getting married to depend on the distance between classes, the stationary wealth distribution crosses over from an exponential to a power-law regime as the number of wealth classes and the level of class distinction increase.

Director alignment at the nematic-isotropic interface: elastic anisotropy and active anchoring.

Activity in nematics drives interfacial flows that lead to preferential alignment that is tangential or planar for extensile systems (pushers) and perpendicular or homeotropic for contractile ones (pullers). This alignment is known as active anchoring and has been reported for a number of systems and described using active nematic hydrodynamic theories. The latter are based on the one-elastic constant approximation, i.e. they assume elastic isotropy of the underlying passive nematic. Real nematics, however, have different elastic constants, which lead to interfacial anchoring. In this paper, we consider elastic anisotropy in multiphase and multicomponent hydrodynamic models of active nematics and investigate the competition between the interfacial alignment driven by the elastic anisotropy of the passive nematic and the active anchoring. We start by considering systems with translational invariance to analyse the alignment at flat interfaces and, then, consider two-dimensional systems and active nematic droplets. We investigate the competition of the two types of anchoring over a wide range of the other parameters that characterize the system. The results of the simulations reveal that the active anchoring dominates except at very low activities, when the interfaces are static. In addition, we found that the elastic anisotropy does not affect the dynamics but changes the active length that becomes anisotropic. This article is part of the theme issue 'Progress in mesoscale methods for fluid dynamics simulation'.

Avaliação da cognição de um grupo de idosos institucionalizados de uma região do norte de Portugal / Cognition assessment of a group of institutionalized aged from a northern region of Portugal / Evaluación cognitiva de un grupo de ancianos institucionalizados de una región del norte de Portugal

Resumo Contexto: Envelhecer compreende um conjunto de alterações, nomeadamente cognitivas; existindo uma linha muito ténue entre as mudanças esperadas para esta etapa da vida e as alterações de cariz patológico. Cerca de 80% das pessoas com défice cognitivo desenvolvem demência, pelo que, é fundamental intervir para retardar o aparecimento desta síndrome. O primeiro passo para a intervenção é a avaliação do perfil cognitivo destas pessoas. Objetivos: Identificar o perfil cognitivo de um grupo de idosos de uma região do Norte de Portugal; e identificar a relação entre as variáveis sociodemográficas e o perfil cognitivo de um grupo de idosos de uma região do Norte de Portugal. Métodos: Estudo quantitativo, transversal, descritivo-correlacional de corte. A amostra foram idosos institucionalizados (n = 37) com capacidade para responder a um questionário composto por questões sociodemográficas e pelo Montreal Cognitive Assessment (MoCA), versão portuguesa. A colheita de dados decorreu entre Novembro de 2017 e Fevereiro de 2018, sendo cumpridos todos os pressupostos éticos da investigação com humanos. Resultados: Os participantes eram maioritariamente mulheres (67,6%), com média de idade de 82 anos, viúvas e com mais de 4 anos de escolaridade. A pontuação obtida no MOCA variou entre 6 e 24 pontos, verificando-se correlação entre o score global e as variáveis sexo e idade. Todos os participantes apresentaram défices maioritariamente na linguagem e na abstração. Conclusões: Evidenciou-se uma maior prevalência de défices cognitivos na população mais velha, sendo clara a importância de avaliar e intervir na cognição destas pessoas, objetivando a manutenção/regressão dos défices e prevenindo a evolução para quadros demenciais. Pela proximidade a esta população, os enfermeiros, nomeadamente os especialistas em saúde mental e psiquiatria, são agentes privilegiados para a intervenção nesta área, através da implementação de programas de estimulação geral da cognição.

Abstract Background: Aging comprises a set of changes, namely cognitive. There is a very thin line between the expected changes for this stage of life and the pathological changes. About 80% of people with cognitive impairment develop dementia, so it is essential to intervene to delay the onset of this syndrome. The first step for the intervention is the assessment of the cognitive profile of these people. Aim: To identify the cognitive features of a group of aged from a region of northern Portugal; and to identify the relationship between sociodemographic variables and cognitive features of a group of elderly people from a northern region of Portugal. Methods: Quantitative, cross-sectional and descriptive-correlational study. The sample consisted of institutionalized aged (n = 37) capable of answering a questionnaire composed of sociodemographic questions and the Montreal Cognitive Assessment (MoCA), Portuguese version. Data collection took place between November 2017 and February 2018, and all ethical assumptions for human research were met. Results: The participants were mostly women (67.6%), with an average age of 82 years, widows and with more than 4 years of schooling. The MOCA score ranged from 6 to 24 points, with a correlation between the overall score and the gender and age variables. All participants presented deficits mostly in language and abstraction. Conclusions: The results confirm the higher prevalence of cognitive deficits in the older population, being clear the importance of evaluating and intervening in the cognition of these people, aiming at the maintenance / regression of the deficits and preventing the evolution to dementia. Due to the proximity to this population, nurses, namely specialists in mental health and psychiatry, are privileged agents for intervention in this area, through the implementation of general cognition stimulation programs.

Resumen Contexto: El envejecimiento comprende un conjunto de cambios, a saber, cognitivos; Hay una línea muy delgada entre los cambios esperados en esta fase de la vida y los cambios patológicos. Alrededor del 80% de las personas con deterioro cognitivo desarrollan demencia, por lo que es esencial intervenir para retrasar la aparición de este síndrome. El primer paso para la intervención es la evaluación del perfil cognitivo de estas personas. Objetivo(s): Identificar las características cognitivas de un grupo de ancianos de una región del norte de Portugal; e identificar la relación entre las variables sociodemográficas y las características cognitivas de un grupo de ancianos de una región del norte de Portugal. Metodología: Estudio cuantitativo, transversal y descriptivo-correlacional de corte. La muestra consistió en ancianos institucionalizados (n = 37), capaces de responder un cuestionario compuesto por preguntas sociodemográficas y la Evaluación Cognitiva de Montreal (MoCA), versión portuguesa. La recopilación de datos tuvo lugar entre noviembre de 2017 y febrero de 2018, y se cumplieron todos los supuestos éticos para la investigación en humanos. Resultados: Los participantes eran en su mayoría mujeres (67,6%), con una edad promedio de 82 años, viudas y con más de 4 años de estudio. El puntaje MOCA varió de 6 a 24 puntos, con una correlación entre el puntaje general y las variables de género y edad. Todos los participantes presentaron déficits principalmente en lenguaje y abstracción. Conclusiones: Los resultados confirman la mayor prevalencia de déficits cognitivos en la población de edad avanzada, dejando en claro la importancia de evaluar e intervenir en la cognición de estas personas, apuntando al mantenimiento / regresión de los déficits y evitando la evolución a la demencia. Debido a la proximidad a esta población, las enfermeras, es decir, especialistas en salud mental y psiquiatría, son agentes privilegiados para la intervención en esta área, a través de la implementación de programas generales de estimulación cognitiva.

Literacia em saúde em pessoas com alterações da saúde mental / Health literacy in people with mental health changes / Alfabetización en salud en personas con trastornos de salud mental

Resumo Contexto: A saúde mental está diretamente relacionada com a literacia em saúde, uma vez que, a primeira é influenciada pela segunda, podendo melhorar ou não a qualidade de vida do indivíduo dependendo da saúde mental de cada um. A literacia em saúde ou alfabetização em saúde pressupõe uma interação entre os profissionais de saúde e os indivíduos. Objetivo: Conhecer o nível de literacia em saúde nas pessoas com alterações de saúde mental assistidos na casa de saúde do Bom Jesus, Braga, Portugal. Métodos: A amostra deste estudo foi constituída por 101 doentes com alterações da saúde mental assistidos numa instituição de assistência psiquiátrica no Norte de Portugal, dos quais 23 eram acompanhados externamente à instituição e 78 estavam institucionalizados em unidades de curto internamento. Resultados : Os resultados obtidos, através da aplicação de um questionário e posteriormente pela análise dos dados, evidenciaram a existência de baixos níveis de literacia em saúde em 71,6% dos inquiridos. Observou-se também a existência de relação entre a idade e as habilitações literárias destas pessoas com o nível de literacia, no entanto, apesar de haver evidência estatística suficiente para afirmar que o nível de literacia em saúde é influenciado pela idade ou pela escolaridade, esta relação é desprezável, fazendo com que não se possa afirmar que, quanto mais velho menor a literacia em saúde ou quanto maior o nível de escolaridade maior o nível de literacia. Também se pode verificar a existência de relação entre o nível de literacia em saúde e as pessoas com o diagnóstico de "perturbação neurótica". Conclusões: Assim sendo, podemos concluir que a literacia em saúde é influenciada pela saúde mental das pessoas. Uma vez que, a segunda influência a qualidade e segurança dos cuidados de saúde das pessoas. É necessário que as pessoas tenham habilidades de inteligência e comunicação para tomarem decisões informadas sobre a melhor decisão a ser tomada em relação à sua saúde.

Abstract Background: Health literacy or basic health knowledge presupposes an interaction between health professionals and individuals. Thus, mental health is directly related to health literacy, since the former is influenced by the second, and may or may not improve the quality of life of the individual depending on the mental health of each one. Aim: To know the level of health literacy in people with mental health disorders assisted at Bom Jesus health home. Methods: The sample of this study consisted of 101 patients with mental health disorders who were taken care of at a psychiatric care institution in northern Portugal, of which 23 were externally monitored and 78 were institutionalized in short hospitalization units. RESULTS: The results obtained, through the application of a questionnaire and later by the data analysis, evidenced the existence of low levels of health literacy in 71.6% of the respondents. It was also pointed out the existence of a relationship between the age and the qualifications of these people with the level of literacy, however, although there is sufficient statistical evidence to affirm that the level of health literacy is influenced by age or schooling, this relationship is negligible, making it impossible to state that the older the people are, the lower level of health literacy they have, or the higher the level of schooling the higher the level of literacy. It is also possible to check the existence of a relationship between the level of health literacy and people diagnosed with "neurotic disorder". CONCLUSIONS: Thus, we can conclude that health literacy is influenced by people's mental health, since, the second influences the quality and safety of people's health care. People should get intelligence and communication skills and abilities to make wise decisions when it comes to make decisions about their health.

Resumen Contexto: La alfabetización sanitaria o la alfabetización sanitaria presuponen una interacción entre profesionales de la salud y las personas. La salud mental está directamente relacionada con la alfabetización en salud, ya que la primera está influenciada por la segunda y puede o no mejorar la calidad de vida del individuo dependiendo de la salud mental de uno. Objetivo: Conocer el nivel de alfabetización en salud en personas con trastornos de salud mental asistidos en el hogar de salud de Bom Jesus. Metodología: La muestra de este estudio consistió en 101 pacientes con trastornos de salud mental atendidos en una institución de atención psiquiátrica en el norte de Portugal, de los cuales 23 fueron seguidos externamente a la casa y 78 fueron institucionalizados en unidades de hospitalización cortas. Resultados: Los resultados obtenidos mediante la aplicación de un cuestionario y análisis de datos posteriores mostraron la existencia de bajos niveles de alfabetización en salud en el 71,6% de los encuestados. Sin embargo, también hubo una relación entre la edad y la alfabetización de estas personas con el nivel de alfabetización, aunque existe evidencia estadística suficiente para indicar que el nivel de alfabetización en salud está influenciado por la edad o la educación. Esta relación es insignificante, lo que hace imposible decir que cuanto mayor es la alfabetización en salud o cuanto mayor es el nivel educativo, mayor es el nivel de alfabetización. También es posible verificar la existencia de una relación entre el nivel de alfabetización en salud y las personas con diagnóstico de "trastorno neurótico". Conclusiones: Por lo tanto, podemos concluir que la alfabetización en salud está influenciada por la salud mental de las personas. Desde entonces, el segundo influye en la calidad y seguridad de la atención médica de las personas. Las personas necesitan habilidades de inteligencia y comunicación para tomar decisiones informadas sobre la mejor decisión con respecto a su salud.

Impact of the Fourth Industrial Revolution on the Health Sector: A Qualitative Study.

OBJECTIVES: The Fourth Industrial Revolution is changing the way health is understood, transforming the methods of treatment and diagnosis as well as the relationship between health professionals and patients and altering the management and organization of health systems. The main objective of this study was to explore the impact that the Fourth Industrial Revolution is having on the health sector. METHODS: Conducting interviews consisting of four questions with 10 professionals who had experience working in the health sector to gain their insights and to obtain information to meet the general objective of the study as well as its specific objectives. RESULTS: From the analysis of the respondents' responses, it was possible to create five dimensions developed by the topics most addressed by respondents, namely, impact on healthcare efficiency and effectiveness, impact on government action, impact on human resources, impact on health system organization, and financial impact on the health sector. CONCLUSIONS: Although the Fourth Industrial Revolution is still at an early stage, it has been concluded that it is having a major positive impact on the health sector. For the effective and efficient implementation of these disruptive technologies, a global interaction between governments, health professionals, stakeholders, and society is essential to make this change possible.

The Cell Adaptation Time Sets a Minimum Length Scale for Patterned Substrates.

The structure and dynamics of tissue cultures depend strongly on the physical and chemical properties of the underlying substrate. Inspired by previous advances in the context of inorganic materials, the use of patterned culture surfaces has been proposed as an effective way to induce space-dependent properties in cell tissues. However, cells move and diffuse, and the transduction of external stimuli to biological signals is not instantaneous. Here, we show that the fidelity of patterns to demix tissue cells depends on the relation between the diffusion (τD) and adaptation (τ) times. Numerical results for the self-propelled Voronoi model reveal that the fidelity decreases with τ/τD, a result that is reproduced by a continuum reaction-diffusion model. Based on recent experimental results for single cells, we derive a minimal length scale for the patterns in the substrate that depends on τ/τD and can be much larger than the cell size.

Unsaturated Response of Clayey Soils Stabilised with Alkaline Cements.

The influence of suction on the mechanical behaviour of unsaturated chemically stabilised soils is still mostly unknown and unquantified. This is also motivated by the difficulties associated with the experimental procedure required to fully characterise the unsaturated response of the soil, including its direct influence on traditional strength tests. The present paper presents the soil water retention curves obtained for a Portuguese soil before and after being stabilised with Portland cement (OPC) and an alkali-activated cement (AAC). Saturated undrained triaxial tests were also performed for the same curing conditions (0, 28, and 90 days). Previous attempts to characterise the retention curve of soils stabilised with AAC are unknown, and the results showed that the pore volume structure is already formed after 28 days, prior to the full development of the gel matrix responsible for the strength increase between 28 and 90 days. The curve changed after stabilisation, and with each binder, as the OPC presented a higher air-entry value and a narrower suction range compared to the AAC solution. The significant differences between the curves obtained from each binder suggest the future development of a methodology to assess the quality of the AAC stabilisation.